boring bar chatter

[chipproducer]

Hi Everyone,

I have started a job, and it went so well to start, but now the boring bar will not stop chattering. We tried changing the insert first, then moved on the speed and feed changes. We even tried changing the depth of cut to no avail.

Thanks



If it would help, I could download pics of the parts.

[Verfur]

If possible shorten the lenght that the tool sticks out and use a positive type insert. General rule of thumb tool stick out less than 4* dia of said tool.

P.S. spindle bearings can play a big part.

Please post pics of Job and set up and materail type.

John

[Walt@SGS.Inc]

This boring bar, is it in a turning center or a machining center?
A little more information could be helpful.
What kind of material etc etc...Regards Walt

[chipproducer]

Sorry guys,

The material is 4130 steel. It is on a lathe and it is as short as it can be already.

Pics to follow soon.

[Verfur]

can it be a bigger tool? and how thin a wall is the part?

[Derek.C]

Try boring from the inside out to try and get under the chatter also an old trick to stop vibration is to wrap the boring bar with elastic bands . Helps absorb the vibration , next step carbide bar.

[dertsap]

try some thick tapping oil , rather than flood coolant ,if that's what you are using , maybe try using a used insert that is in decent shape , sometimes a new insert will chatter until it has some wear on it

[DareBee]

Insert will need a very small nose radius to reduce cutter pressure - say .007 - .015"

[SeaSchell]

Use a positive insert with minimum corner, wrap boring bar and part with rubber bands slow RPM

[rhino]

is the tool on center? how big is the hole you are boring? are you using the largest size boring bar possible? it can be a number of things.

[chipproducer]

having problems posting pics.

The question has more to do with the fact that the first 15 pcs were perfect. Without changing anything, the chatter suddenly became a problem from one piece to the next. Now we can't get rid of it.

[Verfur]

Ah,
I to have run into this situation before on bar stock turnered out to be the material was a little difrent in the mid of the bar stock than on the ends go fiquire like to drove me nutttsssss!!! It could be a chemical dif or mechanical like its ben work hardend. I would try a slighty higher feed rate and or more depth of cut to keep the tool loaded. Also what type of tool (insert) are you using (I.E. CNMG 431, CCGX 430 exc.) pluss lead angle of. Oh and material condition.

Oh ahh is this a first op or 2nd and or 3rd? just asking cause I have seen parts change by diffrent ops, you know one guy may be more agressive than the other and or vis/versa just a thought.

John